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ReadFetch Stateless Change Detection (Diff)
x402
ReadFetch Stateless Change Detection (Diff) is a paid API for AI agents from readfetch.com, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-31).
Detects whether a web page has changed since a previous fetch by comparing a stored hash, and returns a bounded text diff if it has.
Price / call$0.003
Success—
StatusUnknown
How this service works
Stateless change detection: send the hash you hold, get changed/unchanged and a bounded diff. A no-change answer is billable.
Output
Returns a changed/unchanged status flag, a new sha256 hash of the current page content, and (if changed) a bounded diff showing added and removed text segments. If previous_content was provided, the diff includes line-level additions and deletions. An unchanged response is still billable.
Example use cases
Price page change alert
“Has https://competitor.com/pricing changed since yesterday? I have the hash sha256:9f8e7d6c5b4a from my last check — if anything changed, show me what's different in plain text.”
Terms of service update tracker
“Check if https://stripe.com/tos has been updated — my previous hash is sha256:1a2b3c4d5e6f — and give me a diff of any additions or removals so I can flag it for our legal team.”
News article update detection
“I scraped https://bbc.com/news/article-12345 earlier and have the hash sha256:deadbeef1234. Has the article been edited since then? If so, what changed? Use residential egress since the site blocks datacenters.”
Technical details
Endpoint
POSThttps://readfetch.com/v1/diff?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need stateless change detection — you hold the hash from a previous call and want to know if a page changed without the service maintaining session state for you. Ideal for polling workflows where you store the hash on your side and periodically check for updates. Prefer over full-scrape endpoints when bandwidth and cost matter, since an unchanged response is cheap and a changed response gives you only the delta. Use the residential egress option for sites that block datacenter IPs.
Side effects
- URL unreachable or returns non-200 status — endpoint may return an error or empty diff
- Timeout exceeded (max 120s) if the target page is slow to respond
- Residential egress unavailable or blocked by target — may fall back or error
- Hash mismatch due to dynamic page content (ads, timestamps) causing false positives
- Invalid sha256 hash format in previous_hash field causes validation error
- Page content too large for bounded diff — diff may be truncated
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| url | string | Public http(s) page to re-fetch and compare; must match the extraction used when you saved the hash (same `format`). |
| format | string | Extraction flavour for this fetch and for the hash (default text). Must match how you built `previous_content` if you send it. |
| timeout_s | number | Total budget for the whole call in seconds, both fetches included. 60 s is the ceiling on this route. |
| previous_hash | — | `sha256:…` or bare hex from readfetch_diff, readfetch_probe `content_sha256`, or a prior text read. Omit on the first poll to establish a baseline hash in the response. |
| previous_content | — | Full prior extracted text (what you stored from readfetch_text/readfetch_diff). Required for `added`/`removed`/`diff` output; hash-only compares do not emit a line diff. |
Tags
x402
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